149 



Cttherea (Caryatis) plana, Sowerbt. 



Plate 17, figures 14, 14a, and 146. 



Venus planus, Sowerby. — Min. Conch., Vol. I., (1812) p. 58, pi. 20, lower 



figures. 

 Cytherea plana, Goldfuss. — Petr. Germanice, "Vol. II., p. 138, pi. 148, 



fig. 4. 

 Venus plana CSoirerby), B'OThignj. —Pal. Tranc, Terr. Cret., Vol. III., p. 447, 



Atlas, pi. 386, figs. 1-3. 

 Cytherea plana, Sowerbj, Sp. Stoliczka. — Cret. Pelecyp. S. India, p. 169, pi. 7, figs. 1-4 

 ? =Cytherea Leonensis, Conx&d. — Emory's Eep. on the U.S. & Hex. Bound. 



Surv., 1857, Vol. I., p. 153, pi. 6, fig. 1. 

 f=Meretriz Tippana, Conrad. — Jour. Ac. Nat. Sc. Phil., 1858, Series II., 



Vol. III., p. 326, pi. 34, fig. 18. 

 Aphrodina Tippana, Con. — Am. Jour. Conch., 1868, Vol. IV., p. 246, 



pi. 18, fig. 5. 

 Compare also Meretrix nitida, Gftbb. — Pal. Cal., Vol. I., p. 165, pi. 23, figs. 145 and 



146. 

 Caryatis nitida, Gabb. — Id., Vol. II., p.p. 186 and 240, pi. 30, fig. 79. 



Shell modei"ately convex, very inequilateral, variable in outline, but 

 usually ovately subtriangular, length always a little greater than th© 

 height; test rather thick. Umbones broad and tumid in full grown 

 shells, less so in small specimens ; beaks very small, usually depressed 

 but rarely a little elevated, curved inwards, downwards and somewhat 

 forwards, placed at a distance from the anterior end of about one-third 

 the entire length, or less, but never quite terminal. Anterior dorsal 

 slope short, abrupt, and slightly excavated ; posterior dorsal declivity 

 longer, convex, and more gradual in its descent ; outline of the basal 

 margin forming a broad, semi-ovate curve, most prominent a little in 

 advance of the middle ; anterior end narrowly rounded ; posterior end 

 subtruncated. Lunule elongated, lanceolate or lanceolate cordate ; 

 bordered by an impressed line. 



Surface polished, neai-ly smooth, marked by concentric striations, most 

 of which are plainly visible to the naked eye, and on the upper and 

 central parts only of the posterior end by very minute radiating lines 

 which cannot be seen without the help of a lens. Pallial sinus deep, 

 angular, pointed, and extending inwards nearly to the centre of the shell. 



Eight valve with three hinge teeth and a sublunular tooth. The two 

 cardinal teeth are small, short, close together, and slightly divergent ; 

 they are placed immediately under the beaks, and are nearly transverse 

 to the hinge line. The lateral tooth is elongated, oblique, and nearly 



